| 摘要 |
An audio signal amplifying circuit includes a switch circuit disposed between a first power source line and a second power source line for bootstrapping, and a capacitor for bootstrapping disposed between the second power source line and a line to which an output terminal is connected. The switch circuit is controlled from ON to OFF upon receiving a muting signal, and is provided with a first switch circuit constituted by Darlington connected transistors having an NPN type transistor as the output stage thereof and a second switch circuit constituted by a PNP type transistor disposed in parallel with the NPN type transistor. The sum of the rated current values of the NPN type transistor in the first switch circuit and the rated current value of the PNP type transistor in the second switch circuit is selected to be equal to or more than the maximum supply current value for the second power source line, and the rated current of the PNP type transistor in the second switch circuit is selected to be smaller than the rated current values of the transistors in the first switch circuit.
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